Notice that in the dotted line above there is an arrowhead.
There is also an arrowhead on the bottom side of the triangle.
Those arrowheads mean that the dotted line and the bottom side of the triangle are parallel.
Since the bottom side is perpendicular to the left vertical side, then the dotted line is also perpendicular to the left vertical side.
The angle formed by the dotted line and the vertical side is 90 deg.
Since the angle shown is 28 deg, then the upper left angle of the triangle is 90 - 28 = 62 deg.
Now you have enough info to answer the question.
For the 62-deg angle, the 350-ft side is the adjacent leg.
y is the opposite leg.
The trig ratio that relates the adjacent and opposite legs is the tangent.
